A wide variety of vehicles utilize electronic brakes. While these types of vehicle are typically of the class of towed vehicles such as trailers, in certain instances self-powered vehicles may also be provided with electronic brakes. Regardless, however, of whether or not the vehicle is independently operated, operating as a towing vehicle, or operating as a towed vehicle, the application of brakes to that vehicle dictates a consideration of a vehicle's speed, forward or rearward acceleration or deceleration, lateral acceleration or deceleration, as well as the angle, in relation to the horizontal, on which the vehicle may be operating, such as when climbing or descending a hill or other incline.
Brake controllers may be manufactured as a part of the vehicle, or may be independently manufactured and installed in the vehicle as an after-market item. In either event, the function of the brake controller is to apply a suitable amount of braking power to electronic brakes to insure a smooth, safe and controlled stop.
There are a number of problems with existing brake controllers. For example, after-market brake controllers are typically installed in cars, light trucks, or other towing vehicles to provide a braking signal to a trailer being towed by the towing vehicle and attached to the towing vehicle by a trailer hitch or similar mechanical attachment. For very light towed vehicles, it is possible and acceptable to dispense with a separate braking system for the towed vehicle, and, in fact, many lightweight trailers currently in use have no brakes of any kind. However, once the weight of the towed vehicle becomes more substantial, it is desirable to provide the towed vehicle with a separate braking system. While such systems may be hydraulic, pneumatic or electrical, it is generally accepted that electrical braking systems are the most desirable, inasmuch as they are simple to interface with the braking system of the towing vehicle.
In its simplest form, the brake controller used in this environment is a relay or switch which senses the operation of the brakes in the towing vehicle, and thereupon applies braking power to the towed vehicle. Often the controller senses a signal from the towing vehicle by virtue of the fact that the towing vehicle's brakes are operated simultaneously with the towing vehicle's brake lights. By connecting the towing vehicle's brake light circuit to the controller, the controller can be made to operate, and hence send a braking signal to the towed vehicle, whenever the brake lights of the towing vehicle are activated.
Unfortunately, such simple systems are entirely unsuitable for operation in a modern traffic system. It is undesirable that the towed vehicle's brakes be fully applied whenever the towing vehicle's brake light circuit is activated. Under these circumstances, the towed vehicle's fully applied brakes will essentially lock the towed vehicle's wheels, providing substantially more braking than is required and placing enormous stress on the mechanical connection between the towed and the towing vehicle.
It is essential, therefore, that the braking power being applied to the towed vehicle's brakes be proportional to the braking power applied to the towing vehicle's brakes and that the amount of braking power so provided be fully variable. Accordingly, just as an increase in pressure on the brake pedal of a motor vehicle having hydraulic brakes results in gradually increasing braking forces, so must a variable amount of braking power be applied to the electric brakes of the towed vehicle to insure a smooth and safe stop or deceleration.
Fortunately, electrical brakes installed on most towed vehicles are well suited to fully proportional operation. Since the electronic actuators in electronic brakes are capable of providing braking force proportional to the amount of electrical energy supplied, techniques and equipment have been developed to permit the gradual application and gradual release of braking forces to the electronic brakes of such vehicles.
One simple approach has been to provide a control device, such as a potentiometer, which applies a proportional amount of braking to a vehicle's electronic brakes depending on the position of the potentiometer over its range. For such a device to work effectively, however, it is essential that the potentiometer or other variable control be interconnected with the pneumatic or hydraulic brakes of a towing vehicle. Such interconnection requires substantial engineering and assembly effort, and is difficult to accomplish as a retrofit or after-market product. Further, while currently known brake controllers sometimes have such a variable control which can be manually operated, it is difficult to simultaneously apply braking to the towing vehicle (for example, with the foot of the operator), and to achieve comparable proportional braking to the towed vehicle (for example, with the hand of the operator), by operating a manual control on a separate controller device. Inevitably, in these circumstances, either too little or too much braking energy is applied to the brakes of the towed vehicle.
To overcome these problems, modern brake controllers often include a mechanical accelerometer which senses the amount of deceleration of the towing vehicle and applies electrical energy to the brakes of the towed vehicle in an amount proportional to the deceleration of the towing vehicle. In a non-abrupt, mild stop situation, where the towing vehicle may take a long distance to bring the combined towing/towed vehicle to a stop, the accelerometer would sense very little deceleration and apply little or no electrical energy to the brakes of the towed vehicle. By contrast, in an emergency stop situation, the accelerometer senses that the towing vehicle is making an abrupt stop, and accordingly the controller will apply a proportionally higher amount of electrical energy to the brakes of the towed vehicle. While this type of controller is a substantial improvement over the earlier and more primitive controllers, these controllers still tend to under-apply and over-apply forces during braking actions.
The inability of this type of controller to accurately measure acceleration and deceleration is a function of reliance on simple mechanical accelerometers. Presently, brake controllers do not compensate for resistive changes due to heat and the frequency of brake use. The amount of braking required by a vehicle in city driving, characterized by frequent starts and stops, is very different than that required by the same vehicle travel in a highway setting where there are fewer braking events. Further, these controllers are typically capable of measuring only straight line acceleration and/or deceleration, and do not sense or respond to lateral acceleration. Additionally, these controllers are not provided with the ability to sense the inclination of the towing vehicle, i.e., whether the towing vehicle is ascending or descending an incline. The amount of braking energy required to slow a vehicle moving up an incline is substantially less than that required of the same vehicle on level ground. Conversely, the amount of braking energy required for a vehicle descending an incline is substantially higher than that required for a vehicle decelerating on level ground. Finally, this type of controller operates in a temporally limited manner, i.e., it does not store and analyze data regarding vehicle movement and inclination.
Recently brake controllers have been developed which overcome some of these difficulties by using modern multi-axis solid state accelerometers. Robinson, et al., in U.S. Pat. No. 6,837,551, teaches the use of a multi-axis accelerometer in association with a microprocessor to supply braking to a towed vehicle in response to precisely measured acceleration forces in more than one axis. This device, however, uses polling techniques which do not provide enough acceleration data to assure smooth braking. Substantial improvements can be made to the existing art through improved algorithms for analysis of the accelerometer data, specifically by incorporating historical information regarding a towing vehicle's movement in advance of brake operation. By continuously monitoring the acceleration and orientation of the towing vehicle, more effective braking of the towed vehicle can be achieved.
Current controllers provide only limited feedback to the operator as to the condition of the brake controller itself, and the functionality of the brake controller both before and during the braking operation. The present invention provides an alphanumeric and graphical display for providing substantial feedback to the vehicle operator about the braking system.
It is an object of the present invention to provide a means to control the brakes of a vehicle by continuously compiling data regarding the movement and orientation of the vehicle in advance of a braking event.
It is another object of the present invention to provide a brake control device that accurately measures acceleration, deceleration and orientation of a vehicle without reliance on mechanical inputs.
It is further an object of the present invention to provide a controller which provides substantial information to the operator of a towing vehicle regarding the operation of the brake controller.
It is a further object of the present invention to provide a brake system controller which is easily operated by a person in a towing vehicle without the need for manipulation of mechanical controls.
It is a further object of the present invention to provide a brake controller for use in a towing vehicle that assures that the brakes of a towed vehicle are operated accurately and proportionally to the amount of braking energy required in view of the deceleration and/or orientation of the towing vehicle, both automatically, and through manual means.
It is a further object of the present invention to provide a brake controller which does not rely on mechanical inputs such as pneumatic and hydraulic sensors, but which provide superior braking through emulation of this type of mechanical input by simulating those inputs utilizing electronic hardware and software.
It is a further object of the present invention to provide a brake controller that automatically compensates for resistive changes in the braking environment, including heat or other resistive changes to the electrical braking system.
Other objects and advantages of the present invention will be apparent from the following description.